As disclosed in U.S. Pat. No. 5,759,140 assigned to the Assignee of this application, crankshafts may be machined to have oil holes at various angles to the longitudinal axis of the crankshaft and at various rotational positions about the circumference of the crankshaft and spaced lengthwise portions along the length of the crankshaft. The cutting tool is moved along and across the length of the crankshaft to cut a hole anywhere along and across the axial length of the crankshaft. As disclosed in the foregoing patent, the cutting tool travels along a fixed axis and the crankshaft is mounted in a workholder or fixture which turns about a turning axis normal to the longitudinal axis of the crankshaft in order to drill at various angles to this longitudinal axis. Also, the crankshaft is spun about its longitudinal axis to present various peripheral, rotational locations for drilling. The crankshaft is held in a fixture or workholder usually having a pair of crankshafts mounted between headstocks and tailstocks for spinning of the crankshaft and having an open face for permitting the loading and unloading of the crankshaft through the open face. The machine disclosed in the foregoing patent also has an automatic tool changer such as a wine rack to allow it to use different cutting tools and/or bushings or the like for each of the particular hole configurations and multiple tools are disposed side-by-side for traveling along parallel plunging axis to machine a pair of crankshafts at the same time to increase the production of the machine.
The present invention is also related to moving milling machine into engagement with crankshafts or the like to provide milling cutters which cut at an acute angle to the axis but desire to leave a flat, horizontal face on the cam profile such as patents to Phillips U.S. Pat. Nos. 4,551,048 and 4,624,610 and as disclosed in co-pending provisional application, U.S. Provisional Patent Application No. 60/680,934, filed May 13, 2005.
Often crankshafts or camshafts for automobile engines and truck engines or the like are manufactured or machined in large production quantities on multi-station transfer lines. Each station of which is dedicated to machining one or more holes, such as holes in crankshafts or to machining a cam profile on a camshaft. The transfer line works well where the workpiece for a given production model will have identically machined holes or cam profiles for thousands and thousands of workpieces which are machined. Thus, there is a need for a new and improved method and apparatus for drilling the complete crankshaft in one station rather than drilling one hold in each station as in a transfer line.
The drilling of oil holes in crankshafts at precise locations involves drilling into eccentric pin bearings and through main bearings at precisely located positions for the entry point of the hole and the exit point for the hole at various acute angles to the longitudinal axis of the crankshaft. In the aforementioned patented machine, and in other following patented machines, the drilling tool traveled along one of the orthogonal X or Y axis and the entire crankshaft was turned to the desired inclined angle to the tool travel axis in order that the drilled hole be located at the desired acute angle to the crankshafts longitudinal axis. Various tolerances are encountered in precisely positioning the tool entry point, when rotating the crankshaft, shifting the tool carrier and tool between successive oil hole drilling locations, positioning the tool and crankshaft relative to one another at the desired angle, and shifting the tool along its plunging axis at this angle. Hence, it is necessary for a successful, commercial machine to overcome these positioning tolerances in order to accurately locate these holes in the crankshaft at the desired angle, peripheral location and longitudinal offsets.
Moreover, in these commercial machines, the tool is positioned with computer controlled drives using a computer and/or controller and software therefore. Hence, it is desirable for a commercial, production machine to simplify the software needed to locate and position the tool for drilling oil holes at precise included angles, at the predetermined entry and exit points along the crankshaft and at the desired tool entry points on the crankshaft's peripheral surface.